Characterization of glutamate-gated chloride channels in the pharynx of wild-type and mutant Caenorhabditis elegans delineates the role of the subunit GluCl-α2 in the function of the native receptor
Characterization of glutamate-gated chloride channels in the pharynx of wild-type and mutant Caenorhabditis elegans delineates the role of the subunit GluCl-α2 in the function of the native receptor
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DOI：
10.1124/mol.59.5.1037
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发表时间：
2001-05-01
影响因子：
3.6
通讯作者：
Holden-Dye, L
中科院分区：
文献类型：
--
作者：
Pemberton, DJ;Franks, CJ;Holden-Dye, L
谷氨酸门控氯 (GluCl) 通道是驱虫药伊维菌素的作用部位。此前，非洲爪蟾卵母细胞表达系统已被用于表征从秀丽隐杆线虫克隆的 GluCl 通道。然而，缺乏有关天然的药理学相关受体的信息。在这里，我们使用线虫咽部的定量药理学方法和细胞内记录技术来表征它们。谷氨酸反应是一种快速脱敏、可逆、氯依赖性去极化（EC50 = 166 muM），仅被印防己毒素微弱拮抗。激动剂的效力顺序为鹅膏酯 > L-谷氨酸 > 红藻氨酸 = 使君子酸。伊维菌素有效且不可逆地使肌肉去极化 (EC50 = 2.7 nM)。在最大伊维菌素反应期间共同施用最大谷氨酸没有观察到进一步的去极化，这表明伊维菌素通过与谷氨酸（即氯化物）相同的离子机制使肌肉去极化。伊维菌素对咽部的效力大于对非洲爪蟾卵母细胞中表达的任何 GluCl 亚基的效力。伊维菌素的这种作用在突变体 avr-15 中被消除，该突变体缺乏功能性 GluCl-alpha (2) 亚基。然而，对谷氨酸的氯化物依赖性非脱敏反应仍然存在。因此，GluCl-α (2) 亚基赋予伊维菌素敏感性和对天然咽部 GluCl 受体的高亲和力脱敏谷氨酸反应。
Glutamate-gated chloride (GluCl) channels are the site of action of the anthelmintic ivermectin. Previously, the Xenopus laevis oocyte expression system has been used to characterize GluCl channels cloned from Caenorhabditis elegans. However, information on the native, pharmacologically relevant receptors is lacking. Here, we have used a quantitative pharmacological approach and intracellular recording techniques of C. elegans pharynx to characterize them. The glutamate response was a rapidly desensitizing, reversible, chloride-dependent depolarization (EC50 = 166 muM), only weakly antagonized by picrotoxin. The order of potency of agonists was ibotenate > L-glutamate > kainate = quisqualate. Ivermectin potently and irreversibly depolarized the muscle (EC50 = 2.7 nM). No further depolarization was seen with coapplication of maximal glutamate during the maximal ivermectin response, indicating that ivermectin depolarizes the muscle by the same ionic mechanism as glutamate (i.e., chloride). The potency of ivermectin on the pharynx was greater than at any of the GluCl subunits expressed in X. laevis oocytes. This effect of ivermectin was abolished in the mutant avr-15, which lacks a functional GluCl-alpha (2) subunit. However, a chloride-dependent, nondesensitizing response to glutamate persisted. Therefore, the GluCl-alpha (2) subunit confers ivermectin sensitivity and a high-affinity desensitizing glutamate response on the native pharyngeal GluCl receptor.